Impedance matching between a signal processing system and an antenna can be an issue in radio-frequency (RF) integrated circuit applications, like power amplifiers and high frequency transceivers. Impedance matching is accomplished by designing the input impedance of an electrical load to be equal to the output impedance of the signal source to which it is ultimately connected. Impedance matching is usually done to maximize the power transfer and minimize reflections from the load. Lack of impedance matching can cause undesirable power losses, thermal heating, echoes and other issues.
Additional elements are often required inside or outside of the package to obtain the desired matching. External discrete passives and integrated passive devices external or internal to the package can be used as matching elements. These additional elements can consume valuable package area or system board area which can add to the system cost and can also add to the size of the system package. However, it is desirable to minimize both the system cost and size.
Capacitive coupling can be an issue when it is desirable to remove the constant DC components of a signal while transmitting the varying AC components. The resulting signals are sometimes called DC balanced signals. Capacitive coupling is the transfer of energy within an electrical network by means of the capacitance between circuit nodes, and is usually done by placing a capacitor in series in the signal path. The capacitor allows the AC component of the signal to pass across the capacitor but blocks the DC component of the signal. The resulting DC-balanced signals can be useful in communications systems, since they can be used over AC-coupled electrical connections to avoid voltage imbalance problems and charge accumulation between connected systems or components.
It would be desirable to have a methodology to implement electromagnetic coupling in integrated circuit design, such as impedance matching or capacitive coupling, that has a minimal impact on system cost, system size and other desirable factors.